Wireless telephony services have historically treated data and voice transmission differently. This was logical as the demands on such services differed. As data transmission was introduced to mobile telephony networks, it was a low bandwidth solution that was almost an after thought. As voice and data services evolved, voice was still considered as the primary service offered by the network, and certain accommodations were provided to ensure consistency and reliability to the voice network.
In voice communications, dropping a connection is a measure of last resort. It is commonly accepted that a noisy voice connection is preferable to no connection at all. However, data connections are treated differently. Dropping a data connection is often seen as an acceptable action as the data packets missed due to the dropped connection can be retransmitted. This typically is not even noticeable to the user, who at worst will be inconvenienced for a matter of seconds while a dropped data connection is re-established and the data re-requested.
With the arrival of true high speed data networks, such as 1xEV-DO networks, wireless data connections are now suitable for a number of uses that were previously unsuitable to wireless data connections. This has led to an increase in the utility of the wireless data networks.
In 1xEV-DO systems, the common cellular structure of wireless telephony networks is maintained. Each sector is assigned a unique pseudo random number code (PN code). This PN code is used by both mobile access terminals (AT) and the underlying access network (AN) to specify a particular sector in the network.
The AN maintains a list of PNs associated with each AT that has a data connection. This list is mirrored in the AT. The list of PNs forms an active set used by the AT and the AN for transmitting and receiving data packets. During the connection between the AT and the AN, the AT monitors the strength of pilot signals from surrounding sectors. When the pilot strength of any sector crosses a threshold, a route update (RU) message is sent to the AN. Two thresholds are commonly set, a Pilot_ADD and a Pilot_DROP threshold. When a pilot signal is detected with a signal strength higher than the Pilot_ADD threshold the PN associated with the sector transmitting the pilot signal is submitted to the AN as a sector that the AT can access. Similarly, when an already monitored signal is determined to have dropped below the Pilot_DROP threshold, the AN is informed that it can drop the PN from the active set associated with the AT.
The present handling of adding and dropping sectors in networks such as the 1xEV-DO network, often result in dropped data connections. Although in an environment, where the data network is used purely for non-time critical data delivery, this is not a great impediment. However, as data transmission rates have increased, the data network can serve other uses, including time critical uses such as carrying Voice over Internet Protocol (VoIP) based calls and video telephone applications. VoIP calls provide voice service to users over the data portion of the network. VoIP calls can easily be supported by networks such as the 1×EVDO deployments, but cannot offer users the required reliability unless the data connection is as secure as a voice channel. Although dropping a standard data connection, such as a request for a webpage, is only seen as an inconvenience, dropping the data connection that carries a VoIP data stream is equivalent to dropping a voice channel, which is commonly seen as a highly undesirable action. To allow for connection reliant services such as VoIP, a more robust data connection management method is required.
It is, therefore, desirable to provide a method and system for reducing the number of dropped data connections in a wireless data network.